HP to kW Calculator
Convert horsepower (mechanical, electrical, or metric) to kilowatts. Live calculator with exact constants for motor and equipment sizing.
Common conversions
| Input | Result |
|---|---|
| 1 HP (mechanical) | 0.75 kW |
| 5 HP (mechanical) | 3.73 kW |
| 10 HP (mechanical) | 7.46 kW |
| 10 HP (metric PS) | 7.35 kW |
| 20 HP (mechanical) | 14.91 kW |
| 50 HP (mechanical) | 37.28 kW |
| 100 HP (mechanical) | 74.57 kW |
| 200 HP (mechanical) | 149.14 kW |
The math behind it
- kW = 15 × 0.746
- kW = 11.19
Everything you need to know
Multiplying horsepower by a constant converts it to kilowatts, but the constant depends on which horsepower definition applies to your equipment. Three standards exist, and picking the wrong one introduces error before you've even touched a wrench.
Mechanical, electrical, and metric horsepower
Mechanical horsepower (745.7 W) comes from James Watt's original definition and is the figure stamped on most US pump, compressor, and engine nameplates. Electrical horsepower is defined as exactly 746 W and is the constant NEMA uses for AC motor ratings in North America, less than 0.01% different from mechanical HP and effectively interchangeable in practice. Metric horsepower, labeled PS (Pferdestärke) or CV (cheval-vapeur) on European and Asian equipment, equals 735.5 W, about 1.4% lower than mechanical HP. A 100 HP mechanical rating and a 100 PS rating are not the same shaft power; the PS-rated machine is producing roughly 1.1 kW less.
Why US and European nameplates disagree
European manufacturers rate motors, pumps, and engines in kW directly, then back-calculate an approximate PS figure for marketing. US manufacturers do the opposite: they rate in mechanical or electrical HP and treat kW as the export conversion. That's why a 75 kW European motor gets sold in the US market as roughly 100 HP, and why the sizes rarely line up to a clean round number. When you're replacing an imported motor or comparing spec sheets from each side of the Atlantic, convert both to the same unit before comparing frame sizes, current draw, or price.
Shaft output versus electrical input power
HP-to-kW conversion answers only one question: what is the mechanical output at the shaft? It says nothing about how much electricity the motor pulls from the wall. Every real motor loses some input energy to resistive heating in the windings, iron losses in the core, and friction and windage in the bearings and fan. A typical industrial induction motor is 88% to 96% efficient, so electrical input kW is always higher than the mechanical output kW this calculator returns. To estimate input power, divide the converted kW by the motor's efficiency: a 50 HP motor at 91% efficiency needs roughly 40.9 kW of input power, not the 37.3 kW the raw conversion shows. Use the Motor kW calculator when you need that input-side figure for breaker or service sizing.
Common applications
Replacing a 10 HP US motor with a European unit? Order the metric equivalent near 7.5 kW rather than searching for a matching HP nameplate; European catalogs rarely list horsepower at all.
Pump and compressor performance curves are often published in HP, but VFD nameplate parameters and PLC setpoints are entered in kW. Convert the curve's HP figure before programming the drive's overload protection.
Automakers publish electric motor output in kW, while shoppers comparing against a gasoline engine still think in HP. Multiplying the EV's peak kW by roughly 1.34 gives a fair cross-shopping figure.
Customs paperwork and engineering stamps often require both units listed. Converting HP to kW and rounding to two decimals keeps documentation consistent across a fleet that mixes US and imported machinery.
Common mistakes
A 10 HP motor needs about 8.5 kW of electrical input at 88% efficiency, not the 7.46 kW the raw HP-to-kW conversion gives. Skipping the efficiency division under-sizes the breaker and feeder.
Mechanical (745.7 W), electrical (746 W), and metric (735.5 W) horsepower differ by up to 1.4%. Using the mechanical constant on a European PS-rated engine overstates its output by roughly 1.1 kW per 100 PS.
Converting shaft HP to kW tells you mechanical power, not the kWh a utility bills for. Energy cost depends on input kW, efficiency, and hours run, not the shaft rating alone.
Using 0.75 instead of 0.7457 for mechanical HP looks harmless but shifts a 200 HP conversion by nearly 1 kW, enough to push a motor across a standard frame size boundary.
Frequently asked questions
How many kW is 1 HP?+
One mechanical horsepower equals 0.7457 kW. Electrical HP (746 W) equals 0.746 kW, and metric PS (735.5 W) equals 0.7355 kW, all within about 1.4% of each other.
Is HP the same as kW?+
No. HP and kW both measure power, just in different units. One HP converts to roughly 0.75 kW depending on which HP standard applies.
How many kW is a 5 HP motor?+
About 3.73 kW of shaft output. The electrical input is higher, typically 4.1 to 4.4 kW at 85-90% efficiency, because of winding and friction losses.
Does HP-to-kW conversion include motor losses?+
No. The conversion gives shaft output only. Electrical input kW equals HP × 0.7457 divided by the motor's efficiency, typically 0.88 to 0.96 for industrial motors.
Which HP standard should I use for a US motor nameplate?+
Use mechanical or electrical HP (745.7 W or 746 W). Both appear on NEMA-rated equipment and differ by less than 0.1%.
Which HP standard applies to European engines and pumps?+
Metric horsepower, PS or CV, equal to 735.5 W, is the standard on European and most Asian data sheets.
Why does a 100 PS engine convert to less kW than 100 HP mechanical?+
Because metric horsepower is a smaller unit. 100 PS equals 73.5 kW, while 100 mechanical HP equals 74.6 kW, a gap of about 1.1 kW.
Is 1 kW more than 1 HP?+
Yes. 1 kW equals about 1.34 HP, so a kilowatt is the larger unit of the two.
How do I convert a generator engine's HP to its kW rating?+
Multiply the engine's mechanical HP by 0.7457 to get shaft kW, then apply the alternator's efficiency, typically 85-95%, to estimate usable electrical kW output.